//���� cookie ֵ�ĺ���
function setCookie(cname,cvalue,exdays){
  let d = new Date();
  d.setTime(d.getTime()+(exdays*24*60*60*1000));  
  let expires = "expires="+d.toGMTString();
  document.cookie = cname + "=" + cvalue + "; " + expires;
  console.log(cname + "=" + cvalue + "; " + expires);
}

//��ȡ cookie ֵ�ĺ���
function getCookie(cname){
  let name = cname + "=";
  let ca = document.cookie.split(';');
  for(let i=0; i<ca.length; i++) {
    let c = ca[i].trim();
    if (c.indexOf(name)==0) return c.substring(name.length,c.length);
  }
  return "";
}

//��� cookie ֵ�ĺ���
function checkCookie(){
  var username=getCookie("username");
  if (username!=""){
    alert("Welcome again " + username);
  }else {
    username = prompt("Please enter your name:","");
    if (username!="" && username!=null){
      setCookie("username",username,365);
    }
  }
}

function clearCookie(name) {
  setCookie(name, "", -1);
}